Service How To Procedures Hydraulic Counterbalance - Replacement - VMC - AD0289
Last updated: 01/18/2019

Hydraulic Counterbalance - Replacement - VMC

AD0289

Applies to machines built from: May, 1995 to May, 2012

Introduction

Always replace the cylinder and the tank together as a set. If you replace one of these parts without the other, the warranty is void on the replaced part.

Tools Required

  • Charge/Discharge Kit (35-4050A)

Each kit contains :

  1. Hydraulic cylinder
  2. Hydraulic tank 
  3. Hydraulic pressure switch cables

System Overview

  1. Hydraulic fluid tank
  2. Schrader valve
  3. Hose
  4. Hydraulic Cylinder
  5. Bracket for the spindle head casting
  6. Clevis pin and cotter pin

Mechanical Safety

 Caution: When you do maintenance or repair on CNC machines and their components, you must always follow basic safety precautions. This decreases the risk of injury and mechanical damage.

  • Set the main circuit breaker to the [OFF] position.
  • Use an approved lock with an approved safety tag. Always follow lock-out procedures in accordance to local government rules.
  • After turning off the machine, wait at least 5 minutes before working in the control cabinet, to allow power to dissipate. Wait for the voltage indicator LED on the vector drive to go off completely.
  • Always turn off the main air supply when you work on any part of the pneumatic system.
  • Make sure to rest the spindle head on a block of wood when work is done on a vertical axis. This will prevent any unintended movement that could result in the axis falling.
  • Never alter any safety circuits on the machine.
  • Never change any parameter while in DEBUG mode (Classic Haas Control) and the servos ON. Put the machine in Emergency Stop mode to change any parameters.
  • Never operate the machine in DEBUG mode (Classic Haas Control).

You should not do machine repair or service procedures unless you are qualified and knowledgeable about the processes. Serious damage to the machine components can result in costly repairs. The service technicians at your Haas Factory Outlet (HFO) have the training and experience, and are certified to do these tasks safely and correctly. The repair and service work performed by your HFO is protected with a limited warranty.

 Danger:  Some service procedures can be dangerous or life-threatening. DO NOT attempt a procedure that you do not fully understand. If you have any doubts about doing a procedure contact your Haas Factory Outlet (HFO) and schedule a service visit.

System Discharge

1

Jog the spindle head to 14.5" (36.8 cm) above the table.

Put a wood block on the table. Lower the spindle-head casting onto it.

 Note: Do not lower the spindle onto the block.

Push [POWER OFF].

Set the main circuit breaker to the OFF position.

Lock the main circuit breaker. Use an approved lock and an approved safety tag.

Disconnect the two-pin [2] end of the pressure switch cable from the pressure switch.

Remove the cap [1] from the Schrader filler valve.

 Note: If your system has a double-ended tank system, a second Schrader valve is at the top of the tank(s). Remove the cap from the bottom valve.

2

With your fingers, tighten the charge/discharge-kit gas chuck [2] onto the Schrader valve [1].

Put the other end of the hose in a bucket to contain the hydraulic oil.

Slowly turn the T-handle clockwise until the system starts to discharge. The time for this to complete is 10 minutes or less. Make sure the pressure gauge shows 0 psi.

Turn the T-handle fully counterclockwise and remove the gas chuck from the Schrader valve.

Cylinder and Tank Replacement

1

Remove the screws that connect the Z-Axis waycover to the spindle head.

Record the direction the hydraulic hose connection [1] faces.

Remove these hydraulic cylinder parts:

  • Small/medium mill;
    • Cotter pin [5]
    • Jam nuts [4]
    • Washer [3]
  • Large mill
    • Cotter pin [5]
    • Clevis pin [6]

Loosen the (2) screws [7] on the cylinder support bracket. Remove the band clamp [8].

Disconnect the hydraulic hose from the tank.

Remove the hydraulic cylinder [2] from the top of the column.

2

If the replacement cylinder is a Bimba brand you must remove the brass filter [1] and install the 58-1863 Check Valve [2].

Use a dab of Teflon thread sealant on the check valve threads [3].

 Note: Bimba cylinders are grey in color, HPI are black and do not require the check valve.

3

 Caution: Fully clean the mating surface [2] on the mounting bracket for the hydraulic cylinder.

Install the hydraulic cylinder [A] from the top of the column.

 Caution: Make sure the hydraulic hose connection [1] faces the same direction as the one that was removed.

To connect the hydraulic cylinder to the lift bracket:

  • Small/medium mill
    • Pull the piston shaft [3] through the lift bracket [4].
    • Install the washer [5] and (2) jam nuts [6].
    • Install the cotter pin [7].
  • Large mill
    • Pull the piston shaft [3] down until the clevis [8] fits over the lift bracket [4].
    • Install the clevis pin [9].
    • Install the cotter pin [7].

Install and tighten the band clamp [10].

4

Remove the tank assembly from the column.

Remove the tank from the mount.

Install the hose from the new hydraulic cylinder [A] onto the new tank.

Put the hydraulic tank into the tank mount.

Install the hydraulic tank [B] onto the column.

Look at the connector on the pressure sensor cable installed in the machine.

  • If the connector is the same as the connector on the tank [1], use the installed cable.
  • If the connector is not the same as the connector on the tank [1], discard the installed cable. Install the pressure sensor cable [C] or [D] from the kit.

Connect the two-pin end of the pressure cable to the pressure switch on the tank.

5

With your fingers, tighten the gas chuck [1] on the charge/discharge kit to the Schrader valve [2].

 Note: Make sure you turn the T-handle of the gas chuck fully counterclockwise.

 Note: If your system has a double-ended tank system, a second Schrader valve is at the top of the tank(s). Use the bottom valve.

Attach the other end of the hose to the source pressure [3].

Slowly pressurize the system to the correct value. Refer to the chart at the end of this procedure.

Power up the machine.

Push [ZERO RETURN]. Push [Z]. Examine the tank and hoses for leaks or abnormal noises. Make sure the tank pressure is correct at the top of travel. Add nitrogen if necessary. Remove the charging system. Replace the valve cap.

Cylinder - Alignment

If the hydraulic counterbalance cylinder is not correctly aligned, this causes seal distortion [1] and friction to the wear band [2].

This will ultimately cause the cylinder to fail.  Perform this procedure to align the cylinder.

1

Loosen (1) screw on the cylinder mounting bracket.

Make sure the screw is sufficiently tight to hold the cylinder in position, but sufficiently loose to let you make the adjustment.

The illustration shows the cylinder mounting bracket for a large mill [1] and for a small or medium mill [2]

2

Make sure the (2) screws [1] on the bracket are sufficiently tight to hold the cylinder in position, but sufficiently loose to let you make the adjustment.

Put an indicator [2] on the top of the spindle head casting.

Put the tip of the indicator on the front of the cylinder.

Jog the Z Axis to the top of travel. Set the indicator to zero.

Jog the Z Axis to measure the error from the top of the cylinder to the band clamp.

If the indicator moves more than 0.005", lightly tap the cylinder near the support bracket until it is aligned.

3

Put the tip of the indicator [3] on the side of the cylinder.

Jog the Z Axis down to the lowest point that the indicator will reach. Set the indicator to zero.

Jog the Z Axis to measure the error from the top of the cylinder to the band clamp.

If the indicator moves more than 0.005", lightly tap the cylinder near the support bracket until it is aligned.

Tighten the (2) screws [2] on the cylinder support bracket and the (1) screw on the cylinder mounting bracket.

Make sure the cylinder did not move when you tightened the bracket.

If your machine has (2) cylinders, repeat this procedure on the other cylinder.

Counterbalance Pressure Chart

This chart shows the correct pressures for the counterbalance tank. Measure the pressure at the top of Z-Axis travel for VMCs and at the top of Y-Axis travel for HMCs. Pressure that is 50 psi (3 bar) higher than the value in the chart is permitted. But pressure that is lower than the value in the chart is not permitted.

Model Made After Pressure Made After Pressure Made After Pressure
- - PSI BAR - PSI BAR - PSI BAR
EC-1600/2000/3000 3/15/2004 1000 70 9/13/2004 550 38 6/14/2005 800 55
EC-630 3/21/2006 800 55 - - - - - -
HS-1 10/30/1997 600 51 - - - - - -
HS-3/4/7 6/5/1998 1150 79 6/18/1999 1200 83 2/29/2000 1250 86
VB-1 6/5/1998 1550 107 - - - - - -
VF-3/4 (VCE 1000/1250) 4/28/1995 1150 79 - - - - - -
VF-5 XRT 10/8/2004 750 52 - - - - - -
VF-5, VM-3, VF-3YT (VCE 1300) 7/21/1998 950 66 10/14/1998 875 60 - - -
VF-5/50, VF-3YT/50 (VCE 1300) 7/21/1998 1100 76 - - - - - -
VF-6/7/10/12 - 50 (VCE 1600, 2000, 3000) 10/30/1997 1150 79 - - - - - -
VF-6/7/10/12 (VCE 1600, 2000, 3000) 10/30/1997 750 52 - - - - - -
VF-8/9/11 - 50 (VCE 1600, 2000, 3000) 7/21/1998 1550 107 - - - - - -
VF-8/9/11 (VCE 1600W, 2000W, 3000W) 10/30/1997 750 52 - - - - - -
VF-O/OE/EXT/1/2 (VCE 475/500/550/700/750) 4/28/1995 750 52 - - - - - -
VR-8/9/11 10/30/1997 1800 124 7/21/1998 1100 76 10/14/1998 1025 71
VS-1/2/3 2/29/2000 1250 86 - - - - - -
VTC 5/4/2002 1150 79 - - - - - -

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